For strictly convex quadratic functions, we have the following recursive formula for the gradients \(g_k\)  and, as a consequence, for their coefficients (cf., e.g., [1]})
\(\mathbf {g}_{k+1} &= (I - \beta _{k}^{\rm {}} A)\,\mathbf {g}_k, \\\gamma _{i}^{k+1} &= (1 - \beta _{k}^{\rm {}} \lambda _i)\, \gamma _{i}^{k}.\) 
